In modern biotechnological operations, it is often necessary to inject small amounts of protein, DNA, RNA, drugs or other substances into each of a plurality of living cells. For example, quantities such as 20 to 50 nanoliters may be desired to be injected into each of a plurality of frog oocytes. Alternatively, a few nanoliters (1 to 10) may be required to be injected in mouse stem cells. These injections are frequently required to be made quickly and easily into large numbers of cells, for example, into thousands or tens of thousands of cells.
Such injection is presently carried out manually, utilizing micromanipulators to hold micropipettes, and further utilizing a microscope for visual observation. Some mechanization has been developed for such techniques. One device is available under the designation Stoelting Model 567-57-RH. Another is available under the designation Narishigi Model MO203. However, even with such devices, significant manual intervention is required. For example, in one known device, the cells are plated on a cover slip or petri dish. A computer controlled microscope having a TV camera is manipulated by an operator. A joy stick is used to manipulate the device until a cell is observed under a cross hair. The computer is given information to execute an injection program. However, such devices are expensive, do not create regular distributions of cells, operate slowly, and can only inject approximately 2,000 cells per hour. Thus, such devices cannot easily and inexpensively perform injections of tens of thousands of cells.
Moreover, such prior art devices do not work for cells in a suspension but are limited only to cell types which adhere to surfaces. Moreover, requirement of a human operator to identify the location of each of the cells to be injected adds yet a further expense to operation of the devices.
Electroporation is another known technology for introducing molecules into cells. This technique suffers from at least two disadvantages relative to the present invention, however. First, in typical electroporation, the substance to be introduced must be dispersed throughout the suspension medium, thus requiring the use of much more injectant material. Second, electroporation does not introduce material into the nucleus of the cell.
Lyposomes or calcium phosphate precipitation can also be used to deliver certain materials into cells. However, their use is somewhat limited.
Accordingly, there is a need in the prior art for a device which enables a more rapid injection of large numbers of cells, which does not require tedious human intervention, which is inexpensive, which may be disposable, which is highly efficient in the use of injecting solution which may be quite precious, which introduces injected material into the cell nucleus, which does not require the use of any special biological, which can deliver practically any water-soluble material into the cells and is parsimonious in its use of the valuable reagents, and which is constructed entirely of inert, biocompatible materials.